Audio mixer



FIG. 1 is a plan view of audio mixer showing our new design;

FIG. 2 is a bottom view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view thereof. 

The ornamental design for an audio mixer, as shown and described. 